Sister In Law Drama

I am going to try and explain this as objectively as I can.
BIL got engaged 2022, everyone in the family was asked to be in wedding including significant others except me. I was dating the grooms brother (now my fiancé) . My fiancé had vocalized to everyone he had intentions to propose to me but would wait until SIL and his brothers wedding happened. Relationship with SIL was not bad, we saw each other on holidays spoke to each other and she seemed to like me.

I was not asked to be in SILs bridal party. I was heartbroken and expressed my feelings about not being in the wedding to only my partner. It was very hard being left out, I felt like a second class citizen. I did cry but I pulled myself together and did not let anyone else know that. I stayed quiet and attended all SIL events like bridal shower with a smile.
SIL and my fiances brother got married in this year 2023. She did not have me in any bridal activities I was assigned to sit with extended family at the wedding ceremony. It was a very sad experience for me.
2 weeks after SILs wedding like my partner had said he proposed. Such a special moment. Now I amPlanning my wedding I have been asking my bridesmaids and was really struggling if I should include my SIL in my bridal party.
I posted a cute video of the bridesmaids I had asked and the all of a sudden my fiancé gets a text from his father asking if we will put SIL (not blood family) in wedding, my fiancé finally snapped and said “ idk why? SIL did not have (me) in wedding. To which there was no response back to him.
It really upset me that my SIL that did not have me in her wedding, is now making a fuss to the family to the point that she is involving my fiancés brother and father. that I may or may not be putting her in my wedding. Putting pressure on me. Thoughts?